TEHRAN, Jan 7 – Iran warned Saudi Arabia Wednesday to stop working against it as their diplomatic crisis intensified despite efforts to defuse a row that has raised fears of greater regional instability.

As its diplomats arrived home after being told to leave by Saudi Arabia, Shiite-dominated Iran fired the latest verbal salvo in a dispute that has seen Riyadh and some Sunni Arab allies cut diplomatic ties with Tehran.

At a press conference in the capital, Foreign Minister Mohammad Javad Zarif said Riyadh must end prolonged efforts to confront Iran.

Citing longstanding differences that became a full-blown split after Saudi Arabia executed Shiite cleric and activist Nimr al-Nimr, Zarif said the Sunni-ruled kingdom had sought systematically to inflict damage.

“For the past two-and-a-half years, Saudi Arabia has opposed Iran’s diplomacy,” he said at the press conference with Iraqi Foreign Minister Ibrahim al-Jaafari.

“Saudi Arabia has moved against our efforts and, unfortunately, they opposed the nuclear agreement,” Zarif said, also accusing Riyadh of “taking measures against the Iranian people” through its efforts to keep oil prices low.

“This trend of creating tension must stop. We need to stand united… and stop those who are adding fuel to the fire,” he added.

The spike in tensions comes after Iran last year secured a historic nuclear deal with world powers led by the United States, causing major concern in longtime US ally Riyadh.

That deal, when finally implemented, will end sanctions on Iran’s oil and gas industry and could see the Islamic republic challenge Saudi Arabia’s role as the Middle East’s dominant energy and economic power.

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– Saudi cuts oil price –

Oil prices have fallen by more than 60 percent since mid-2014 as OPEC kingpin Saudi Arabia refuses to lower production in a bid to push competitors out of the market, hurting the income of other producers, including Iran.

On Tuesday, Riyadh cut the February price of its export oil to Europe in another move to win market share.

Nimr’s death sparked demonstrations in many countries including Iran, where protesters stormed and set fire to the Saudi embassy in Tehran as well as the kingdom’s consulate in second city Mashhad.

Riyadh cut ties with Tehran in response and was joined by some of its Sunni Arab allies including Bahrain and Sudan. The United Arab Emirates also downgraded relations with Iran and Kuwait recalled its ambassador.

Djibouti, the tiny Horn of Africa nation, said Wednesday it too had broken diplomatic ties with Tehran.

And Qatar recalled its ambassador while Jordan summoned Tehran’s envoy to protest the attacks on Saudi missions.

Staff at Iran’s embassy in Riyadh and its consulate in Jeddah flew home Wednesday, Saudi state news agency SPA reported.

The dispute has raised fears of an increase in sectarian tensions in the Middle East that could derail efforts to resolve pressing issues including the wars in Syria and Yemen.

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The United Nations and Western governments have expressed deep concern, urging both sides to reduce tensions.

US Secretary of State John Kerry has made repeated calls to both Iranian and Saudi leaders urging calm.

Saudi Arabia and Iran are on opposing sides in some of the Middle East’s worst conflicts.

In Syria, Iran is supporting the government of President Bashar al-Assad against rebel groups, some backed by Saudi Arabia.

And in Yemen, Riyadh is leading a military intervention against Iran-backed Shiite rebels who have seized control of large parts of the country.

– Iran-linked ‘terror’ cell –

Within hours of the embassy attack, Iran’s President Hassan Rouhani called the violence “totally unjustified” but accused Saudi Arabia Tuesday of focusing attention on the incident to “cover its crime” of executing Nimr.

Zarif reiterated that the embassy’s ransacking had no official blessing. “All Iranian officials condemn it,” he said.

Rouhani wrote to Iran’s judiciary chief Wednesday urging a quick and conclusive case against 50 persons accused of involvement in the embassy attack.

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Iraq’s Jaafari, who was to also hold talks with Rouhani, said Baghdad was seeking a potential diplomatic role to help resolve the crisis and echoed the concerns about sectarianism.

“I have spoken to the foreign ministers of some of the Arab countries to reduce the consequences of this issue and prevent enemies from dragging the region into a war that can have no winners,” Jaafari said.

Shiite-majority Iraq has close ties with Tehran.

About 2,000 members and supporters of powerful Iraqi Shiite militias demonstrated in Baghdad Wednesday against Nimr’s execution.

In a further sign of tensions, Sunni-ruled but Shiite-majority Bahrain said it had dismantled an Iran-linked “terror” cell that was planning attacks in the kingdom.

The cell was allegedly linked to Iran’s Revolutionary Guards and Lebanon’s Tehran-backed Hezbollah militia and planning a “series of dangerous bombings” on the tiny Gulf kingdom, the interior ministry said.

Nimr, one of 47 men executed Saturday, was a driving force behind 2011 anti-government protests in Saudi Arabia’s Eastern Province.

He was arrested in 2012 after calling for two governorates to be separated from the kingdom.